Flue gases of industrial furnaces commonly contain a severely corrosive amount of fly ash and sulfur-containing gases and particularly sulfur oxides such as SO.sub.2 and SO.sub.3. When such sulfur containing flue gases contact an uncoated interior metal surface of a chimney or stack, particularly under high temperatures above about 200.degree. F., the interior stack surfaces are severely corroded within a short period of time. Accordingly, it is a common practice to wet scrub a flue gas for sulfur removal not only to meet the governmental pollution standards but also to protect the interior stack surfaces. Commonly, in industries such as power generation stations where it is known that there will be a relatively high percentage of sulfur in the flue gases, and where very tall, i.e. 600 foot stacks are necessary, the interior surfaces of these stacks may be lined with super stainless steel which will not rust even under very extremely corrosive conditions. However, sections of the stainless steel stack linings must be welded, and the weld locations become an extremely desirable attack site for high temperature catalyzed chemical corrosion.